This application claims the priority of Korean Patent Application Nos. 2002-81865, filed on Dec. 20, 2002 and 2003-15360, filed on Mar. 12, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a field emission device and a method of manufacturing the same, and more particularly, to a field emission device in which the stability and uniformity of electron emission are improved, and a method of manufacturing the same.
2. Description of the Related Art
Carbon nanotube (CNT) performs field emission even at a very low voltage due to their small diameter and sharp end and has physical characteristics similar to fullerene (C60). Since they have an excellent electron emission characteristic and chemical and mechanical durability, their physical properties and applications have steadily been studied. A Spindt-type field emitter uses a micro-tip as an emitter for emitting electrons. The emitter has a problem in that the life span of a micro-tip is shortened due to atmosphere gases or a non-uniform field during a field emission operation. In addition, with such conventional metal emitter, a work function must be decreased to decrease a driving voltage for field emission, but there are limitations. To overcome this problem, a field emission array (FEA) using carbon nanotubes which have a substantially high aspect ratio, an excellent durability due to their structure similar to that of C60, and an excellent electron conductivity as an electron emission source have been studied.
A field emission array (FEA) using an electron emission material mixture paste and a method of manufacturing the same are disclosed in U.S. Pat. No. 6,440,761. A field emission array using CNTs manufactured by growth as an emitter and a method of manufacturing the same are disclosed in U.S. Pat. No. 6,339,281. In general, it is easier to form the emitter using a paste than by growth. Thus, the former method disclosed in U.S. Pat. No. 6,440,761 is generally preferred.
A CNT emitter formed by these conventional methods is formed on a cathode or a high conductivity material layer formed on the cathode. FIG. 1 shows a traditional example of a conventional triode-type CNT FEA.
Referring to FIG. 1, a cathode electrode 2 is formed on a substrate 1, and a gate insulating layer 3 is formed on the cathode electrode 2. A through hole 3a is formed on the gate insulating layer 3 and a CNT emitter 5 formed of a plurality of CNTs is provided on the bottom of the through hole 3a. The CNT emitter 5 is formed on the cathode electrode 2 exposed to the bottom of the through hole 3a. A gate electrode 4 having a gate hole 4a through which electrons are extracted from the CNT emitter 5 is formed on the gate insulating layer 3.
The CNT FEA has the advantage of achieving electron emission from the entire emitter, unlike in the Spindt-type field emission emitter using a micro-tip. As such, a large amount of electron emission can be achieved. However, actually, electron emission is not performed in the entire emitter but is intensively performed only in part of CNTs. Due to intensive electron emission caused by these CNTs, the uniformity of electron emission and current density are lowered. The uniformity of electron emission and the current density affect the degree of brightness and uniformity of a screen in an image display. The CNT emitter is formed of a paste containing a CNT and a photosensitive resin. A resistive material and a conductive material are mixed with the paste such that electrons are emitted from a front end of a CNT 5a, as shown in FIG. 1. In this case, the FEA has a problem in that current is supplied to the CNT 5a through many conductive paths and electron emission is actually performed only in part of CNTs. Due to electron emission from the limited CNTs, partial overcurrent is generated in the CNT emitter. Thus, the CNTs where electron emission occurs rapidly wear and are damaged. Due to the damage of the CNT, picture quality is lowered, and the life span of the FEA is shortened.